Trident at Risk? UMV Technology vs Submarine Stealth

There has been some speculation that new underwater technologies will soon be able to expose ‘stealthy’ nuclear-powered ballistic missile submarines, thus rendering the UK’s submarine-based Trident system obsolete. In this essay, Ian Keddie considers the various theories and developments. He concludes that critical submarine vulnerability is still several decades away.

The debate over the United Kingdom’s independent nuclear deterrent was reinvigorated when Jeremy Corbyn took over as leader of the Labour Party in 2015. Since the late 1980s, official Labour policy has been to maintain the deterrent. However, the party’s stance on nuclear weapons has shifted under Corbyn, a long-time member of the Campaign for Nuclear Disarmament (CND).

The Corbyn shadow cabinet launched a defence policy review in January 2016, under then shadow defence secretary Emily Thornberry. The report was put on hold because of the disruption following the EU referendum. In the run-up to this year’s general election, the party did outline defence policies in its manifesto, released in May. The manifesto revealed that the party was committed to the Trident system. In subsequent interviews, however, Jeremy Corbyn refused to say whether that would be based on the status quo of four submarines.

Labour’s stance was further confused by a statement from Emily Thornberry, now shadow foreign secretary, who implied that the party might not follow through on the Trident commitment, should Labour come to power. The replacement shadow defence secretary, Nia Griffith, rebuked Thornberry’s comments, insisting that the matter had been settled. “Last year we looked at it, in particular at the national policy forum, and it was decided that we would keep the nuclear deterrent, and that was reaffirmed at our conference in September”, she said.

Jeremy Corbyn outlining Labour’s defence and foreign policy priorities in a speech at Chatham House. May 2017. Image: Chatham House [CC BY 2.0]

In the midst of Labour’s internal squabbles, a vote to replace the existing fleet of Trident missile-carrying Vanguard-class submarines was held in the House of Commons, on 18 July 2016. It passed with a majority of 355, backed by almost the entire Conservative party and more than half of Labour MPs. The vote in parliament appeared to put the matter to bed, especially with little sign that Labour could come into power any time soon.

However, the turbulence of Brexit, and the subsequent snap general election, have made the possibility of a Labour government more likely than many pundits had assumed. Trident, seemingly a settled issue last year, remains a major political issue in the UK, particularly as the Labour party’s stance remains muddied. In Scotland, the Scottish National Party remain committed unilateralists.

Trident, seemingly a settled issue last year, remains a major political issue in the UK, particularly as the Labour party’s stance remains muddied. In Scotland, the Scottish National Party remain committed unilateralists.

Opponents of the UK’s nuclear deterrent have many different reasons for arguing against the Trident programme. The case put forward is often built around costs or requirements for maintaining such a system. Labour’s own aborted review uncovered the idea that future developments in technology, both sub-surface and surface, may eventually uncloak ‘stealthy’ ballistic missile submarines (SSBNs), thus rendering them obsolete. Unmanned maritime vehicles (UMVs) – unmanned underwater vehicles (UUVs) in particular – have attracted considerable interest due to their increasing use, and the advancement of their technology. The idea that these developments will lead to a ‘transparent ocean’ has now become central to arguments against the UK procuring a successor to the current Vanguard-class submarines.

THE NEW TECHNOLOGIES

UMVs – a collective term for any uninhabited system which operates in the maritime environment – are extremely diverse in size, complexity, and function. They have served industrial and scientific uses since the 1960s but were of limited use to the military until more recent decades. Industrial applications were the key drivers behind the research and development of UMV technologies. Remotely Operated Vehicles (ROVs), for example, have been integral to the advances in the deep-water offshore oil and gas sector. UMV technology has become more capable in the last decade, however. Advances in battery life, communications, and processing power have opened up new possibilities for the employment of unmanned systems by the military.

Existing applications of UMVs by navies across the world include mine countermeasures (MCM), explosive ordnance disposal (EOD), and deep water rescue or recovery. Anti-submarine warfare (ASW), intelligence surveillance and reconnaissance (ISR), and rapid environmental assessment (REA) are widely regarded as future applications. It is the area of ASW that has gathered the most attention recently, particularly the prospect of deploying vast numbers of cheap and persistent UUVs equipped with new sensor technology. Opponents of Vanguard replacement have argued that the imminent realisation of this technology will make SSBNs vulnerable, and that a UK deterrent founded on the platform is, therefore, untenable.

SSBN VULNERABILITY

The strategic nuclear forces of several countries use SSBNs to carry out ocean patrols for extended periods. In the case of the UK, this means that a Vanguard-class sub departs its home base in the Firth of Clyde and remains submerged in the Atlantic for a period of some three months as part of the UK’s policy of continuous at sea deterrent (CASD). Navies which carry out SSBN operations, particularly CASD operations, invest a huge amount of effort to ensure that the submarine can complete each patrol undetected and uninterrupted. For these boats, stealth is critical.

The biggest threat to an SSBN has always been that of a nuclear-powered, but not nuclear-armed, attack submarine (SSN) which could match the endurance and stealth of the SSBN. The fear that an SSBN could be unknowingly targeted by a hostile SSN led to a huge effort being put into anti-submarine warfare (ASW) operations during the Cold War.

Successful ASW is a notoriously difficult art to master; it requires sustained effort and the long-term commitment of a substantial number of assets. Even when committing the full spectrum of ASW assets – patrol aircraft, frigates, and SSNs – an ASW operation can only be successful for a short period of time, normally focused on the protection of a specific asset, or confined to an extremely limited area. By the end of the Cold War, western nations had established a primacy over the Soviet Navy in this sphere. They were able to deploy their SSBNs on long patrols, confident that they would remain undetected.

A K-114 Tula nuclear submarine berthed at a pier of the Russian Northern Fleet’s naval base in the Murmansk Region. One vulnerability of advanced submarines is that we know where their bases are. Image: Mikhail Fomichev [CC BY-SA 3.0]

The SSBN departing from port is at high risk because its movements are more easily anticipated. We know where ports are. Geography restricts an SSBN’s effectiveness until it reaches the depths of the open ocean. The Soviet Navy was hampered in its employment of SSBNs for CASD due to a lack of ports that remained ice-free all year. The conditions in the high North restricted the basing of SSBNs and forced them to access the Atlantic Ocean through a limited number of geographic choke points, the so-called Greenland-Iceland-UK (GIUK) Gap. The US Navy established a network of hydrophone arrays called sound surveillance system (SOSUS) to exploit this handicap faced by the Soviet Navy.

Today, many people see parallels with SOSUS and the new UMV technologies. Assuring that an SSBN avoids detection and cannot be targeted is the key principle of CASD. Any threat to this integrity is a serious concern. Many ongoing research projects are seen as likely to deliver new capabilities into the hands of the submarine-chaser: none more so than the proliferation of vast numbers of networked, inexpensive, and autonomous UUVs.

Assuring that an SSBN avoids detection and cannot be targeted is the key principle of CASD. Any threat to this integrity is a serious concern.

In the US, a Darpa research programme known as distributed agile submarine hunting (DASH), which incorporates transformational reliable acoustic path system (TRAPS) and submarine hold at risk (SHARK), has carried out testing of fixed passive sonar nodes and advanced UUVs equipped with active sonars. Other promising work comes from the exploitation of magnetic fields through research into superconducting quantum interference devices (SQUIDS) that could revolutionise the magnetic anomaly detection (MAD) method also used in ASW.

It is claimed that even more effort is being put into this field by countries such as Russia and China, and that it will be their exploitation of new ASW technology that will put SSBNs at risk of detection in the coming decades. When she was Labour shadow defence secretary, Emily Thornberry elaborated on comments that drones could render a successor SSBN obsolete by stating: “If technology is moving faster, it may well be that Trident is not going to be able to hide. If we are to bet everything on mutually assured destruction, we have to be assured it is going to work. If it cannot hide any more, that is a problem.”

PREDICTING FUTURE THREATS

There have been many predictions of the impending transparency of the world’s oceans due to various technological developments. However, these predictions fail to grasp the complexity of ASW operations. They also ignore the limitations imposed by physics. Speaking at Undersea Defence Technology 2016 in Oslo, Rear Admiral Simon Williams outlined the consensus of a panel of industry experts that, whilst new UUV technologies will inevitably change how submarines operate, the likelihood of transparent oceans is unlikely in the foreseeable future. “It is certainly possible but it’s a question of probability”, he said.

There have been many predictions of the impending transparency of the world’s oceans due to various technological developments. However, these predictions fail to grasp the complexity of ASW operations. They also ignore the limitations imposed by physics.

The Admiral went on to outline that “the cost of trying to achieve that is, I think, almost unimaginably expensive because of the number of assets that you would have to use”. He conceded that there is a fixed lifespan to how the underwater domain is currently employed and configured. He concluded that considering the impact of technology is critical to “rethinking our concepts of operations, rethinking what this is going to look like in 50 years’ time, because that’s the likely endurance of our platforms”.

Aside from Darpa’s DASH project, other significant research includes light detection and ranging (LIDAR) and non-acoustic technologies such as chemical or radiological. But despite this advanced research, there remains a large gap between research and actual practical application. It is not certain that any current research will deliver practical applications. Many approaches to advanced ASW technology will lead to dead-ends due to engineering that is too difficult to achieve, or because they are cost prohibitive. The principal research behind SQUIDS, for example, dates back to the 1960s.

At the end of the Cold War, there was much interest in the research that had been done in the former Soviet Union. It soon became apparent however, that much of the Soviet research on alternate ASW detection, such as MAD, had ultimately failed to provide a significant breakthrough. For western navies in the post-Cold War era, it was forecast that UMV technology would deliver a fundamental change in mine countermeasure (MCM) operations. Navies began to incorporate UUVs and USVs, developments were made in creating vehicles that could sweep a minefield without risking a manned vessel; the so-called ‘man out of the minefield’ concept. But more than 25 years later, MCM operations have seen limited adoption of UMVs, despite significant improvements in UMV capabilities.

MODEST PROGRESS

There is little evidence that research in China and Russia matches the levels of investment already seen in the West. China in particular has carried out very little original research, preferring to develop indigenous versions of existing technology. In August this year, there was fresh interest in announcements of Chinese advances in UMV technology; articles reported that a new glider would allow China to instantly detect foreign (American in this case) submarines, and were thus likely to render expensive submarines obsolete almost overnight.

In fact, the story originated from announcements made by the Chinese Academy of Sciences (CAS) about the successful testing of a glider that spent extended periods at sea. Whilst this was indeed a breakthrough for CAS, it actually highlighted precisely how far behind China is in respect to UMV technology. These types of AUVs have been widely used for decades by Western research and commercial outfits.

Progressive improvements to existing technology should be expected as the commercial development of processors, communications, and battery technology becomes ever cheaper. But this fails to address the fundamental limit of physics – the transmission of energy through water, and the high energy demand of movement in water.

Even for the West, the levels of investment in the most promising fields are extremely limited. Progressive improvements to existing technology should be expected as the commercial development of processors, communications, and battery technology becomes ever cheaper. But this fails to address the fundamental limit of physics – the transmission of energy through water, and the high energy demand of movement in water.

Whilst some LIDAR can travel very short ranges in water, only ultra-low frequencies of EM can transmit significant distances. This leaves sound as the primary tool for detection, communication, and navigation in the oceans. Glider-type AUVs are remarkably capable of using the energy of the ocean itself for motion, but these are usually limited to speeds of around 1 knot and are inevitably at the whims of currents and weather. This has proven extremely useful for scientific surveys but it makes their utility for naval use extremely limited. Conventional propulsion UUVs have also improved, but battery life still limits their endurance to a span of hours before they need to be recovered.

PREDICTING FUTURE LIMITATIONS

It is tempting to imagine that utilising UUVs will somehow overcome the limitations of the oceans, and will alter the way that ASW operations are carried out. The problem is that endurance and speed, as well as the size of the oceans, are all in favour of the SSBN. In addition, UMV – and especially UUV – technology can be utilised by the submarine itself for deception or self-defence.

The considerable advantages that SSBNs hold when operating in the open ocean have made them enormously difficult to track. A new generation of persistent, numerous, and interconnected UMVs are inevitably on the horizon and they will certainly present new challenges for both SSNs and SSBNs. But the scale of the oceans and the realities of physics will remain a huge hurdle in terms of broad-area surveillance using UMVs. Also, navies who want to protect their SSBNs will not remain static in developing countermeasures and improving the ability of a submarine to hide.

To have a network of UUVs that could sustain this kind of activity in an ocean like the Atlantic would likely number into the millions – this would be both conspicuous and nearly impossible to maintain.

Whilst ASW forces will benefit from large numbers of inexpensive UUVs – as well as improvements to existing sensors – limitations on energy density in batteries, and maintaining a persistent communication link, will hamper their ability to ‘chase’ an SSBN. What is more probable is that UUVs will be able to act as a semi-permanent barrier, or be quickly deployed in the latter stages of an ASW operation. In order to counter the nuclear deterrent of an adversary, it would be necessary to have continuous, and reliable, surveillance on a patrolling submarine for months or even years. To have a network of UUVs that could sustain this kind of activity in an ocean like the Atlantic would likely number into the millions – this would be both conspicuous and nearly impossible to maintain.

All existing SSBN operators continue to see this platform as the best method for ensuring the survivability of a strategic deterrent. Developing, building, and operating a credible SSBN force is also the most difficult option when compared to a land or air-launched weapon. Acquiring a force is the aim for many existing nuclear powers, most notably China and India. Chinese SSBNs have gone to sea but not yet entered full CASD patrols, despite regular predictions that they will. It is safe to assume the Chinese navy will implement CASD patrols in the foreseeable future: this suggests that the Chinese leadership has confidence that their considerable investment in an SSBN capability will be secure in the long term.

PREDICTING FUTURE RELEVANCE

Submarines operate in every environment offered by the world’s oceans and seas: from the cold, empty, depths of the North Atlantic to the warm, busy, archipelagos of Southeast Asia. Broadly speaking, submarines are used to carry out strategic or tactical tasks. The differences in mission profile and vessel capability means that tactical operations are usually short-term and close to shores or straits. Strategic operations are long-term and occur in large, deep areas of the ocean in order to deter an enemy, or to occupy a desired position in case of conflict.

The greater prospects for UMV technology, and its impact on ASW, lie in focused tactical operational scenarios, against SSNs or conventionally-powered submarines (SSKs), particularly when they are deployed in or around geographic chokepoints or in shallow and acoustically challenging waters. The supremacy of a submarine can be contested in environments like these. A fleet of UUVs could, in these specific circumstances, act as a tripwire to warn of submarine movements in a certain strait and allow an ASW task group to intercept.

The impact of UMV technology is far more likely to be in littoral areas, and in tactical submarine operations, rather than in the vast, deep oceans that strategic submarines inhabit. UMV improvements and future developments will certainly influence SSBN design and doctrine, as have ASW improvements in the past. But they will remain just one set of factors among many to be considered.

Sensors and UMV technology will be more accessible to smaller navies in the future. The SSN in particular will be vulnerable when operating in a tactical role. It is larger and slightly noisier than a SSK and will likely prove to be a hindrance with the proliferation of UMV technology. It is also likely that using a SSN for close-to-shore surveillance operations will become too risky, particularly when compared to using a cheaper and smaller SSK.

The SSBN is the foundation of security for many nations and planning around this capability is considered in lifetimes rather than the next defence review.

Further development of UMV and associated technologies will almost certainly create profound changes to how ASW is executed by navies in the coming decades. Yet submarines and countermeasure technology will not stand still. The SSBN is the foundation of security for many nations and planning around this capability is considered in lifetimes rather than the next defence review.

Inevitably, it will become much harder to hide in parts of the world’s oceans and seas. But even partial ocean transparency would not be enough to render the SSBN obsolete. Reliably tracking and intercepting a single SSBN would still be an immense task for any navy to undertake. Unforeseen breakthroughs in artificial intelligence, quantum fields, or cold fusion, could well deliver a technology that heralds the demise of the SSBN. For now however, it is much more likely that the platform will continue to endure well into the second half of this century.

Ian Keddie is a Toronto-based journalist who specialises in defence, international relations, and technology. He creates original articles and analysis on emerging naval and aerospace technology as well as global military capabilities. Ian was previously the editor of Jane’s Unmanned Maritime Systems and he served as a Lieutenant in the Royal Navy. Contact him at: ianjkeddie@gmail.com Find him on Twitter at: @IanJKeddie